The MOS (metal-oxide-semiconductor) transistor is one of the most important elements in modern integrated circuits. The basic structure of the MOS transistor includes a semiconductor substrate, and a gate structure located on the surface of the semiconductor substrate. And the gate structure includes: a gate dielectric layer located on the surface of the semiconductor substrate; a gate electrode layer located on the surface of the gate dielectric layer; and a source and drain doped region located in the semiconductor substrate at the two sidewalls of the gate structure.
With the development of semiconductor technology, the control capability of the traditional planar MOS transistor on the channel current is weakened, and serious leakage current is produced as a result. The fin field effect transistor is an emerging multi-gate device, the semiconductor substrate generally includes a fin structure which protrudes out of the surface of the semiconductor substrate, a gate structure covering the top surface and the sidewalls of the fin, and a source and drain doped region located in the fin portions on the two sides of the gate structure.
With the further development of the semiconductor technology, there are higher requirements for control capability of the channel current for not only the planar MOS transistor but also the fin field effect transistor. For this reason, a semiconductor device with an ultra-thin channel was used. However, the performance of conventional semiconductor devices having an ultra-thin channel still needs to be improved. The disclosed devices and methods are directed to at least partially alleviate one or more problems set forth above and to solve other problems in the art.